1. Field of the Invention
The present invention relates generally to radiation detecting apparatus, methods of producing the apparatus, and a radiographic imaging system and, more particularly, to radiation detecting apparatus for medical use or for nondestructive inspection, methods of producing the apparatus, and a radiographic imaging system incorporating the apparatus.
In the present specification the description will be given on the assumption that radiations embrace all radiations including X-rays, xcex1 rays, xcex2 rays, xcex3 rays, and so on.
2. Related Background Art
In recent years, imagery is quickly changing from analog images to digital images in the X-ray roentgenologic fields of medical equipment. The digital images allow image processing, which can enhance diagnostic accuracy. Since there is no need for development, radiographic intervals can be shortened and thus radiography can be efficiently performed in group examination and the like.
Requirements in such fields are improvement in detection sensitivity and reduction in noise of signal. Particularly, the improvement in detection sensitivity will result in decreasing X-ray exposure doses during radiography and, in turn, reducing influence on human bodies, so that there are increasing demands for development of X-ray detecting apparatus with high sensitivity.
Technologies necessary for enhancement of sensitivity of X-ray detectors include the following.
(1) Increase in absorption efficiency of X-ray absorbing material
(2) Increase in volume of X-ray absorbing portion
(3) Increase in transfer efficiency of carriers generated in the X-ray absorbing portion
For the increase in the absorption efficiency of the X-ray absorber, attention is being focused on employment of monocrystalline semiconductors such as compound semiconductors and the like. The monocrystalline compound semiconductors have high efficiency of utilization of detected X-rays, because they can produce carriers without conversion to light upon direct absorption of X-rays. Recently, development is under way to develop X-ray detectors with a large area, particularly, sensors associated with the roentgenographic fields, by coupling a monocrystalline semiconductor substrate to a TFT matrix panel.
However, when an area sensor to detect X-rays is fabricated in such structure that TFT portions, transfer lines, etc., together with X-ray sensors, are integrated in a monocrystalline semiconductor being an X-ray absorbing material, absorption of X-rays causes variation in noise and/or capacitances and also causes leakage or the like of TFTs, thus making it difficult to implement the area sensor at a level of practical use. It is thus desirable to produce the monocrystalline semiconductor substrate for detecting X-rays and a substrate having other components of TFT portions and others using a-Si with little absorption of X-rays, separately from each other. After the two substrates are produced separately, they are bonded to each other and on that occasion electrical connection needs to be established at every pixel, however. This makes it difficult to maintain electrical insulation between adjacent pixels in implementation of high-definition radiation detecting apparatus. It is, therefore, an object of the present invention to provide radiation detecting apparatus constructed so as to establish excellent, electrical connection at every pixel and maintain electrical insulation between adjacent pixels on the occasion of bonding the TFT matrix panel side to the monocrystalline semiconductor substrate side.
In order to accomplish the above object, the present invention provides a radiation detecting apparatus in which a first substrate comprising converting means for converting a radiation to charge is bonded through a transfer member for transferring the charge, to a second substrate comprising processing means for processing the charge transferred from the first substrate, wherein an organic film is formed so as to cover a circumference of the transfer member placed between the first and second substrates.
Further, each of the first and second substrates is provided with a passivation film, and the organic film is provided so as to contact each said passivation film, so as to enable bonding without clearance, which is preferable in terms of height adjustment or protection. Moreover, when the first and/or the second substrate is divided into plural segments, the apparatus can be fabricated at good yields, and this structure also facilitates height adjustment during bonding, which is preferable.
The above object is also accomplished by a radiation detecting apparatus having a first substrate comprising means for converting a radiation to charge and a second substrate having a plurality of pixels formed in a matrix pattern, said first substrate and second substrate being electrically connected to each other, wherein a passivation film is provided at least on a surface of the first substrate on the side where the first substrate is connected to the second substrate, an electroconductive adhesive is provided corresponding to the pixels, and on the occasion of coupling the first and second substrates through the electroconductive adhesive to each other, the passivation film is disposed so as to prevent the electroconductive adhesive from establishing electrical conduction between adjacent pixels.
A production method of radiation detecting apparatus according to the present invention comprises a step of forming a passivation film on a first substrate comprising converting means for converting a radiation to charge, a step of forming a passivation film on a second substrate comprising processing means for processing the charge transferred from the first substrate, and a step of placing an organic film on the passivation film formed on the first or second substrate.
Further, a radiographic imaging system according to the present invention comprises the aforementioned radiation detecting apparatus, signal processing means for processing a signal from the radiation detecting apparatus, recording means for recording a signal from the signal processing means, display means for displaying a signal from the signal processing means, transmission processing means for transmitting a signal from the signal processing means, and a radiation generating source for generating the radiation.
The details will be described in embodiments below.